There is known in the art a telephone that can use plural telephone numbers to make or receive a call. For example, in recent years, many mobile phones are equipped with an IC card, referred to as a SIM card (Subscriber Identity Module Card), on which there is recorded a unique ID, IMSI (International Mobile Subscriber Identity), that identifies a telephone number so as to enable the mobile phone to make or receive a call. In a mobile phone equipped with a SIM card, there is read from the SIM card an IMSI that identifies a telephone number assigned to the mobile phone, so as to enable a call to be made or received. On some SIM cards plural IMSIs may be recorded; and a mobile phone including a SIM card on which plural IMSIs are recorded can selectively use the IMSIs to make or receive calls.
In a telephone capable of using plural telephone numbers to make or receive calls, inconvenience is caused if an inappropriate telephone number is selected. Japanese patent document JP 2013-042455 A1 is an example of a document that proposes a technique for eliminating such an inconvenience, by which technique a telephone including a VoIP (Voice over Internet Protocol) function that sends a call via an IP (Internet Protocol) network, notifies a destination telephone of a telephone number as a caller ID that is retrieved from a SIM card, instead of a telephone number of an IP telephone. According to the technique disclosed in Japanese patent document JP 2013-042455 A1, a destination telephone that has received a call made using an IP telephone number receives notification of a telephone number retrieved from a SIM card as a caller ID, so that a user of the destination telephone, who does not know the IP telephone number of the source telephone, can identify a caller of the source telephone.